[Transmission electron microscopy in the structural study of superparamagnetic contrast agents for MRI].

Iron oxide nanoparticles with different crystal sizes and uniform dextran coating were synthesized and analyzed by T.E.M.. The iron oxide core dimension and homogeneity of the preparation were correlated to magnetic properties. The increasing Fe/Dextran ratio used for the synthesis was well correlated with the mean diameter and the magnetic susceptibility. The comparison of the crystal size with the particle size determined by nanosizer in solution suggest that particles consist in nanoaggregates of many crystal subunits.